A union representing American Airways pilots has added its voice to the growing calls not to make public the cockpit voice recorder from United Airlines flight 93, the hi-jacked aircraft that crashed in a Pennsylvania field on 11 September 2001. The debate comes as a feature film about the flight is causing controversy over its trailer and promotion.

Last week the US Appeals Court ruled that any evidence used in open session of the trial of alleged foiled al-Qaeda aircraft hi-jacker Zacarias Moussaoui, would enter the public domain. This could include cockpit voice recorders, in which the pilots are understood to be audible immediately prior to Moussaoui's co-conspirators seizing control of the aircraft by force.

On Friday the Allied Pilots Association (APA), which represents AA's pilots, joined forces with the Air Line Pilots Association (ALAPA) to back groups representing families of the passengers killed in the incident. A 2003 US Congressional report found that four terrorists intentionally crashed the Boeing 757 into fields in Stoney Creek, Pennsylvania due to pressure from passengers to retake the aircraft, which they had intended to crash into the White House in Washington, DC. All 40 passengers and crew were killed in the crash.

To date, only family members of those lost on UA 093 and investigation authorities have heard the tape. The pilots unions are calling for the tape to be played only in closed session. If the tapes were made public, it would set a new precedent and ALPA and APA are concerned other black box recordings could be made public as a result. "Any public release would violate privacy promises made by our government to our nation's professional pilots and set an unfortunate precedent where other cockpit voice recordings are concerned," says Capt Ralph Hunter, APA president.